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An impounded flying saucer, perhaps? Nope! A vacuum tank at the John H. Glenn Research Center.

To celebrate previous April Fool’s Days, we’ve delved into various scientific conspiracy theories on our Bruce science blog. This year we’re doing something similar, but narrowing our focus. Instead of plucking theories from all across the spectrum, this time we’re looking at variations on a particular subject: Aliens!

People have dedicated their lives to proving the existence of extraterrestrial life, though some go about it in a more scientifically rigorous manner than others. In this article, I’ll delve into some of the popular ideas people have about aliens, whether they come from movies, conspiracy theories, or just false assumptions.

Please note: In this discussion, I’m using the word “theory” to mean an unsubstantiated conjecture, not as an established scientific explanation (like the theory of gravity or evolution).

Aliens building the pyramids? Nope! An art installation at the Burning Man Festival. Image by Jennifer Morrow

Did Aliens Build the Pyramids?

There are a lot of conspiracy theories surrounding pyramids, both those in Egypt and around the world. Two very common theories regarding pyramids and alien involvement include:

The pyramids in Giza are far too large and complex to have been built using the technology the Ancient Egyptians had access to. Extraterrestrials must have helped build them.

There are too many similar four-sided pyramids among unconnected ancient cultures to be a coincidence. Aliens must have visited these cultures and spread the art of pyramid-building.

What does science say about these assertions?

Building a pyramid is too difficult for ancient humans.

Though gaps in our knowledge still exist, we do know quite a bit about how the pyramids were constructed. Ancient Egyptian artwork portrays giant stone blocks being placed on sledges and pulled over wetted sand. Scientific analysis has confirmed that this method could have worked. Wetting Egyptian sand dramatically slashes the amount of friction a sledge experiences, enough that they could have pulled a block using half as many people.

Once the blocks arrived at the pyramids, there were ramps to guide them skyward. Egyptologists still aren’t quite sure of the exact design of the ramps, however, and this is still an area of active research.

And how many people would you need to build the Great Pyramid of Giza? Recent research suggests between 20,000 – 30,000 workers were involved in its construction, and that it took about 23 years to build. Compared to Notre Dame, which took about 200 years to complete, the pyramids were constructed in a flash! They were hefty undertakings, certainly, but well within the realm of human ingenuity.

There are square pyramids all over the world. Must be aliens.

The Egyptian pyramids might be the most famous, but other pyramids were constructed in Mexico, Indonesia, Spain, Iran, Cambodia, Greece, and all sorts of other places around the world. When compared to each other, many of these pyramids are eerily similar in shape. Considering that these cultures were separated by oceans and often thousands of years, how is it possible that the pyramids look so alike? Could it be that they were all building the same shape because aliens told them to? Why would so many cultures build pyramids if not motivated by an extrinsic force?

Physics.

If you want to stack stone blocks in a way that is both tall and very stable, you can’t get much better than a pyramid. If you are just building a vertical column, even if you are exceptionally careful with balance, there is still a limit to how high you can stack. The higher the stack gets, the more pressure will be put on the bottommost block in the tower. Eventually, the base block’s compressive strength will be overwhelmed, causing the base to shatter and topple the stones.

If instead of making a column you start stacking your blocks in a pyramid shape, the calculations change. When the bottommost block in a column is put under pressure from blocks above it, it expands slightly outwards horizontally. In a pyramid, the blocks at the base are surrounded by other blocks, which prevent their outward expansion. This strengthens them and allows them to carry more compressive pressure. Pyramids are also very bottom-heavy. The lighter weight on top is able to distribute force more evenly over the wide base.

Overall, pyramids are incredibly strong and stable structures. Humans are intelligent and innovative, so it’s not surprising that people from so many different cultures were able to discover this property of pyramids and build accordingly.

Besides, there are plenty of rectangular temples and tombs all over the world too, and we don’t believe aliens were somehow involved in their creation, do we?

Death by Alien Bacteria

War of the Worlds original illustration.

According to the War of the Worlds, even if humanity is conquered by an alien military force, fear not! The aliens will be wiped out by terrestrial pathogens. Alternatively, in The Andromeda Strain, the human race falls under assault from a bizarre crystalline extraterrestrial microbe. The core belief behind both permutations of this theory is that:

Humans and aliens will be incredibly vulnerable to each other’s diseases, because they have not been able to acquire immunity against them.

Intuitively, this sounds correct. History has shown time and time again that when isolated human groups are exposed to new diseases that they can suffer immense losses. However, there is one important difference between making contact with a human from another civilization and meeting an alien with a cold: Humans are human.

Not every bacteria is dangerous. Out of the many thousands (or perhaps even millions) of bacteria species on Earth, only a small handful are capable of infecting people. For the most part, the bacteria that are dangerous to us are ones that have spent millions of years co-evolving with us or similar animal species on Earth. Infectiousness requires such a specific set of adaptations that it rarely happens by accident.

If bacteria want to invade a human cell, first they have to bind to the surface of that cell. In order to bind, they must recognize specific proteins or carbohydrates on the cell’s surface. It’s not enough for them to be able to recognize something sort of like a human cell. If bacteria have evolved to recognize cat proteins and infect cats, it’s highly unlikely that it would be able to make the leap to infecting humans instead.

If bacteria evolved on another world, it would be virtually impossible for them to recognize and bind to a human cell. However, for the sake of argument, let’s say they manage. What then?

The alien bacteria still wouldn’t get far.

Bacteria require very specific conditions to thrive. Just like you couldn’t drop an unprotected human to the bottom of the ocean and expect them to raise a family, if you take a bacteria that has evolved to live in the soil and inject it into a human, it generally won’t last long.

Though there are bacteria in just about every environment imaginable on Earth, the range at which those bacteria function best is relatively narrow. The bacteria that infect humans unsurprisingly function best in temperatures that approximate normal human body temperatures. They are so strongly adapted to these conditions that even raising the body’s temperature by just a few degrees can slow their reproduction. This is exactly why people grow feverish when sick. By raising the temperature of the body, the bacteria infecting it are weakened and more easily dealt with by the immune system.

So, if an alien bacterium was able to get inside a human cell, unless the alien’s biology was virtually indistinguishable from that of a human, the alien bacteria would fail to thrive.

Humans can infect other humans because the bacteria they’re sharing are uniquely adapted to humanity. In very rare cases diseases can make the jump between animals and humans, but this becomes less likely the further apart evolutionarily the two species are. It would be almost impossible for an alien bacterium to infect a human, and vice versa, simply because the biology is too different between the two organisms.

This is both good news and bad news. We won’t get ravaged by diseases from space, but neither will aliens get struck down by the force of our microbes. Worried about alien viruses instead of bacteria? Don’t be! Viruses also need to recognize specific attachment sites to bind and infect, so the chance of an alien virus being able to recognize a human cell is near zero too.

Extraterrestrial Land Grab

The icy surface of Enceladus

This is a myth about aliens most commonly seen in various blockbuster films, like Independence Day. According to this myth, the Earth is a tempting target for alien invasion because it has so many great resources, such as water and metals. Humans are currently occupying the Earth, meaning that an extermination mission would be first on the to-do list for aliens interesting in turning the planet into a strip mine.

The Earth is a pretty amazing planet with its bounty of life, but it is much less unique where material wealth is concerned. If an alien race found themselves in the neighborhood of our solar system and wanted water, there are plenty of pit stops they could make without having to hassle humans.

The solar system is actually full of water. Numerous moons past the asteroid belt are covered in thick layers of ice, and some even are thought to have layers of liquid water under the surface. An alien race could easily mine water from Enceladus, Ganymede, Europa, and Calisto without having to worry about human invervention.

If its metals the aliens are after, Venus also has a sizeable metallic core, as do Mars and Mercury. Asteroids aren’t as big as planets, but they certainly can be rich in metals as well and are there for the taking. There are even some human scientists who are trying to come up with ways we might mine some of the bounty from asteroids ourselves in the future.

In short, if aliens are after resources, they could easily find just about anything else they wanted elsewhere in the solar system and could leave humans alone entirely.

If it’s the entire Earth package they want, a world where water can exist in liquid form on the planet’s surface, they still have no reason to bother us. There are an estimated 11 billion Earth-like planets orbiting sun-like stars in the Milky Way Galaxy. If the aliens could make it to Earth, certainly they would have the technology to find some other planet among billions to colonize, one that wasn’t already populated by a race fiercely determined to protect it.

Image by Harpagornis

There are many other interesting questions about extraterrestrials that have been explored by science, but one of the most compelling is also the simplest: Is there life on other planets? Thus far, the Earth appears unique among the multitudes in the life that it bears. However, we may be far less alone than it seems.

According to the late Stephen Hawking:

If the argument about the time scale for the appearance of life on Earth is correct, there ought to be many other stars, whose planets have life on them. Some of these stellar systems could have formed 5 billion years before the Earth. 

There are billions of planets within our own galaxy that have the potential to host life. Within the entire universe, that number becomes incalculable. However, what portion of planets with life have species that have achieved sentience? That could be a far lower number. It took about 3 billion years for life on Earth to evolve multicellular animals. That’s an immense stretch of time, and it took a few lucky jumps in evolution to become possible. On many alien worlds, life might never evolve beyond the single-celled phase.

Even if multicellular life does evolve, there is nothing that guarantees that intelligence will eventually arise on a planet. Evolution doesn’t have a goal, except survival. Human evolution is closer to a lucky accident than inevitability.

However, in the near infinite worlds out there, it is entirely likely that there are other intelligent races. Maybe many! Will they ever make it to Earth, and what will happen if they do? That’s a topic for another article.